Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (244 commits)
  Revert "x86, bts: reenable ptrace branch trace support"
  tracing: do not translate event helper macros in print format
  ftrace/documentation: fix typo in function grapher name
  tracing/events: convert block trace points to TRACE_EVENT(), fix !CONFIG_BLOCK
  tracing: add protection around module events unload
  tracing: add trace_seq_vprint interface
  tracing: fix the block trace points print size
  tracing/events: convert block trace points to TRACE_EVENT()
  ring-buffer: fix ret in rb_add_time_stamp
  ring-buffer: pass in lockdep class key for reader_lock
  tracing: add annotation to what type of stack trace is recorded
  tracing: fix multiple use of __print_flags and __print_symbolic
  tracing/events: fix output format of user stack
  tracing/events: fix output format of kernel stack
  tracing/trace_stack: fix the number of entries in the header
  ring-buffer: discard timestamps that are at the start of the buffer
  ring-buffer: try to discard unneeded timestamps
  ring-buffer: fix bug in ring_buffer_discard_commit
  ftrace: do not profile functions when disabled
  tracing: make trace pipe recognize latency format flag
  ...
This commit is contained in:
Linus Torvalds
2009-06-10 19:53:40 -07:00
130 changed files with 9011 additions and 3004 deletions

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Event Tracing
Documentation written by Theodore Ts'o
Updated by Li Zefan
1. Introduction
===============
Tracepoints (see Documentation/trace/tracepoints.txt) can be used
without creating custom kernel modules to register probe functions
using the event tracing infrastructure.
Not all tracepoints can be traced using the event tracing system;
the kernel developer must provide code snippets which define how the
tracing information is saved into the tracing buffer, and how the
tracing information should be printed.
2. Using Event Tracing
======================
2.1 Via the 'set_event' interface
---------------------------------
The events which are available for tracing can be found in the file
/debug/tracing/available_events.
To enable a particular event, such as 'sched_wakeup', simply echo it
to /debug/tracing/set_event. For example:
# echo sched_wakeup >> /debug/tracing/set_event
[ Note: '>>' is necessary, otherwise it will firstly disable
all the events. ]
To disable an event, echo the event name to the set_event file prefixed
with an exclamation point:
# echo '!sched_wakeup' >> /debug/tracing/set_event
To disable all events, echo an empty line to the set_event file:
# echo > /debug/tracing/set_event
To enable all events, echo '*:*' or '*:' to the set_event file:
# echo *:* > /debug/tracing/set_event
The events are organized into subsystems, such as ext4, irq, sched,
etc., and a full event name looks like this: <subsystem>:<event>. The
subsystem name is optional, but it is displayed in the available_events
file. All of the events in a subsystem can be specified via the syntax
"<subsystem>:*"; for example, to enable all irq events, you can use the
command:
# echo 'irq:*' > /debug/tracing/set_event
2.2 Via the 'enable' toggle
---------------------------
The events available are also listed in /debug/tracing/events/ hierarchy
of directories.
To enable event 'sched_wakeup':
# echo 1 > /debug/tracing/events/sched/sched_wakeup/enable
To disable it:
# echo 0 > /debug/tracing/events/sched/sched_wakeup/enable
To enable all events in sched subsystem:
# echo 1 > /debug/tracing/events/sched/enable
To eanble all events:
# echo 1 > /debug/tracing/events/enable
When reading one of these enable files, there are four results:
0 - all events this file affects are disabled
1 - all events this file affects are enabled
X - there is a mixture of events enabled and disabled
? - this file does not affect any event
3. Defining an event-enabled tracepoint
=======================================
See The example provided in samples/trace_events

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@ -179,7 +179,7 @@ Here is the list of current tracers that may be configured.
Function call tracer to trace all kernel functions.
"function_graph_tracer"
"function_graph"
Similar to the function tracer except that the
function tracer probes the functions on their entry

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The power tracer collects detailed information about C-state and P-state
transitions, instead of just looking at the high-level "average"
information.
There is a helper script found in scrips/tracing/power.pl in the kernel
sources which can be used to parse this information and create a
Scalable Vector Graphics (SVG) picture from the trace data.
To use this tracer:
echo 0 > /sys/kernel/debug/tracing/tracing_enabled
echo power > /sys/kernel/debug/tracing/current_tracer
echo 1 > /sys/kernel/debug/tracing/tracing_enabled
sleep 1
echo 0 > /sys/kernel/debug/tracing/tracing_enabled
cat /sys/kernel/debug/tracing/trace | \
perl scripts/tracing/power.pl > out.sv